Non-flexible coatings such as sol-gel coatings and ceramic coatings are widely used on various devices, including domestic appliances such as irons and personal care appliances such as hair rollers. In the field of irons, coatings are applied on a sole plate of an iron in order to impart functional properties. For example, the glidability of an iron may be improved by having a coating on the sole plate. Furthermore, the coatings are applied for decorative purposes. Common materials of the sole plate include aluminum and aluminum alloys, due to their good heat transfer properties. Stainless steel can also suitably be used, due to its pleasing appearance. For this reason, stainless steel sole plates are mostly uncoated. However, such sole plates are less scratch resistant and have poor gliding, in particular on polyester fabrics.
Currently, various embodiments of iron sole plates exist. In one of the known embodiments, the sole plate only has a block of die-cast aluminum. In another of the known embodiments, besides an aluminum block, a thin metal plate is provided, which is attached to the aluminum block. There are various ways of attaching the thin metal plate to the aluminum block, as will be elucidated below, the thin metal plate being referred to as ironing plate.
In the first place, it is common practice to have an aluminum ironing plate, which is attached to the aluminum block by means of rivets and/or paste. During the attachment process, the ironing plate remains flat and does not experience any mechanical deformation. In the second place, the ironing plate may be a stainless steel plate. In that case, it is preferred for the ironing plate to have bent edges, which are used for attaching the ironing plate to the aluminum block by mechanically pressing and rolling the bent edges around the sole plate. In other words, the stainless steel ironing plate is wrapped around the aluminum block.
As stated in the foregoing, when stainless steel is applied, there is normally no coating. Nevertheless, embodiments having a coating are known in the art. For example, WO 98/13544 discloses an iron having a sole plate consisting of an aluminum block, wherein a thin stainless steel plate is secured to the sole plate. In this respect, beading, gluing together and applying mechanical fastening means such as screws, rivets etc. are mentioned as feasible ways in which the attachment of the thin stainless steel plate to the aluminum block may be effected. A manufacturing process of the known iron involves steps of providing the thin stainless steel plate with an anti-friction layer on one side and securing the thin stainless steel plate, with the uncoated side, to the aluminum block.
In respect of the anti-friction layer as mentioned, WO 98/13544 discloses that a sol-gel process may be used to apply the layer. Furthermore, WO 98/13544 discloses that the layer can be made in a thickness ranging from 10 to 25 micrometers, and that the thickness should in practice be less than 20 micrometers, since, as stated therein, undesirable crack formation in the layer may occur at higher thicknesses.
WO 02/066728 discloses an iron having a coated ironing plate, wherein the sol-gel coating may have a higher thickness, namely a thickness ranging from 35 to 90 micrometers. In this iron, the sole plate comprises aluminum, in accordance with what is known from WO 98/13544. Furthermore, a porous layer of aluminum oxide is provided in order to improve adhesion of the sol-gel coating to the sole plate, so that there is no risk of peeling off of the sol-gel coating. In particular, when the sol-gel coating is applied over the porous layer of aluminum oxide, the coating penetrates into the pores of the aluminum oxide, thereby creating some kind of interpenetrating network.
U.S. Pat. No. 6,895,700 discloses a sole plate which is directly provided with a sol-gel coating, wherein a surface to which the coating is applied is hardened, and the application of an ironing plate is omitted. The thickness of the layer is kept below 10 micrometers. U.S. Pat. No. 6,895,700 discloses that by doing so, a shock applied to the coating is transmitted to the hardened metal of the sole plate, which can safely resist shocks of substantial magnitude, so that breakage or deformation of the coating is prevented.
U.S. 2003/074814 discloses an iron comprising an aluminum soleplate which is provided with a coating which is provided by means of a sol-gel process. In particular, the sol-gel coating has a thickness of 35 to 90 micrometers.
DE 44 11 790 discloses an iron comprising an aluminum soleplate that is attached to a block consisting of a silicon-containing aluminum casting. The attachment is realized through a heat-resistant adhesive. Furthermore, it is possible that the attachment is additionally realized in a mechanical manner, namely by means of tin flaps which are part of the soleplate, and which are bent around the block during a manufacturing process of the iron.
EP 0 206 121 discloses that a process such as sandblasting may be carried out prior to a process for coating a domestic utensil, in order to ensure sufficient fixation of the coating.
EP 0 640 714 discloses an iron comprising a metal soleplate which is provided with an anti-friction layer of an inorganic polymer, which is provided by means of a sol-gel process.